Vacuum coating apparatus



A ril 23, 1963 R. v. D. STRONG VACUUM COATING APPARATUS Filed Nov. 9, 1959 INVENTOR. RICH ARD V. D. STRONG M Aw ATTORNEY United States The present invention is directed to vacuum coating apparatus, and more particularly to apparatus for coating articles, such as a web of material, with a metal or the like which has been vaporized in a vacuum.

In the vacuum coating of articles by contact with vaporized material from a boat or reservoir of molten material, severe difficulties have been encountered due to the diffusion of the material being vaporized to the feed source. For example, in the vaporization of aluminum or zinc, where the same is introduced as a wire into a boat, deposition of the vaporized aluminum or zinc on the means for introducing the wire to the boat has caused clogging and jamming of such means and resultant failure of the apparatus. Since satisfactory commercial production requires the continuous adding of material to be vaporized to the boat, the diffusion of such material to the feed source and clogging of the introduction of the feed has prevented efiicient commercial utilization of vacuum coating techniques where vacuum coating for protracted periods of time is desired.

The present invention has as an object the provision of a novel vacuum coating apparatus.

The present invention has as another object the provision of a vacuum coating apparatus in which the supply of the material to be vaporized may be constantly replenished so that the vacuum coating apparatus may be onstream for protracted periods of time.

This invention has as another object the provision of vacuum coating apparatus in which the loss of vaporized coating material on the feed source is minimized.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in the drawings forms which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.

FIGURE 1 is a schematic elevational View of a presently preferred embodiment of the vacuum coating apparatus of the present invention.

FIGURE 2 is a fragmentary plan view revealing the operation of the wire feed.

FIGURE 3 is a sectional view taken on line 33 of FIGURE 1.

FIGURE 4 is a view taken on line 4--4 of FIGURE 3.

FIGURE 5 is a sectional view taken on iine 55 of FIGURE 2.

FIGURE 6 is a view similar to that of FIGURE 3 showing a modified embodiment in which reclamation of coating metal from the shield is effected.

Referring to the drawings, wherein like reference characters refer to like parts, the vacuum coating apparatus of the present invention comprises an outer vessel 10 having a base 12, sides 14 and 16, and a ceiling 18. The entire interior of the outer vessel 10 may be evacuated to a high vacuum through the conduits 20 and 20a in the side 16. Thus, the conduits 20 and 20a may be connected to a vacuum system (not shown) whereby the interior of the outer vessel 10 may be evacuated.

A wide variety of outer vessels may be utilized, as will be readily understood by one having skill in the art, and accordingly the detailed construction of the outer vessel 10 will not be set forth herein. It is, of course, to be understood that the outer vessel 10 includes means for atent O v asserts Patented Apr. 23, 1963 obtaining access to its interior, so as to permit repairs and replacement, while at the same time permitting a vacuumtight seal to be obtained when the interior of the outer vessel 10 is evacuated.

'The understructure designated generally as 22 may be movably supported on the base 12. A wide variety of understructmres may be utilized, and no claim is made as to any specific understructure construction. Preferably the understructures 22 should comprise a plurality of threaded standards 24, each of which should be threadably received within nuts carried by the bed plate 26. In this manner, the height of the support plate 28 in respect to the base 12 may be selectively regulated.

The base 12 may be provided with guide ways 30 and 32 for permitting the transfer of the understructure 2-2 and the material carried thereon along the surface of the base 12.

The support plate 28 carries the means for feeding the material to be vaporized as well as the processing chamher.

The material to be vaporized is preferably in the form of a wire coil, such as the wire coil 34 carried on the spool 36. For the purposes of illustration, in the example set forth herein, the wire coil 34 will be referred to as a coil of aluminum wire 38.

The spool 36 is r-ota-tably mounted, as on trunnions, intermediate the standards 40. The standards 40 are carried on the support plate 28, and are rigidly connected to spaced standards 42 by the connecting arm 44.

A shaft 46 is supported in bushings 48 and 50 above the standards 40 and 42. The rack 52. having an internal bore is clamped on the shaft 46 which extends through its bore. The rack 52 and shaft 46 are recipro-cated in bushings 48 and 50, as will be explained below.

The segment gear 54 is pivotably carried in respect to its gear-support 56 on the pivot 58. Thus, the segment gear 54 is provided with a collar which rotates about the pivot 58. The gear-support 56 is carried on the connecting arm 44. A lever 68 is rigidly secured to the collar of the segment gear 54 which embraces the pivot 58. The free end of the lever 60 is coupled to the compression coil spring 62, The collar of the segment gear 54 also carries the link 64 on which is mounted outside of vessel 10 the cam follower 66. The action of the compression coil spring 62 urges the cam follower 66 against the heart shaped cam 68.

The heart shaped cam 68 is rotatab-ly mounted on the outside of vessel 10 on the shaft 70 which carries the sprocket 72. The sprocket 72 is driven by the chain drive 74 which is coupled to the sprocket 76 of the gear box 78 which is rotated by the motor '80. The engagement between the cam follower 66 and the rotating heart shaped cam 68 will give a uniform oscillating motion to the segment gear 54, which will result in the uni-form movement of the rack member 52 on the shaft 46.

The aluminum wire 38 is urged towards the processing chamber 82 by means of the feeder 84. The feeder 84 includes a pair of vertically spaced rotating members, be tween which the wire 38 is passed, namely the driver 86 and the idler 88. Preferably the driver 86 is provided with a knurled outer surface, .and the idler 88 is formed with a smooth surface. The inlet 90 to the feeder 84 comprises a relatively large bore guide tube, while the outlet 92 of the feeder 84' is coupled to the feed duct 94. The feed duct 94 comprises a metal tube of relatively small inside diameter. Preferably, the feed duct 94 is lined with a self-lubricating material 95, such as the plastic Teflon, a tetrafluoroethylene polymer, to facilitate the movement of the wire '38 therethrough.

Since the feeder 84 is fixedly secured to the rack-member 52 it is reciprocated therewith upon the movement of the segment gear 54.

The rotation of the knurled driver 86 by which the aluminum wire 38 is urged through the feeder 84 is ac- Complished notwithstanding the movement of the feeder 84 in the manner set forth below.

The knurled driver 86 is carried at the end of the rod 96 on which is carried one member of the universal joint 98. The other member of the universal joint 98 is fixedly secured to the coupling rod 106 of the spline coupling 102. The spline coupling 182 also receives the coupling rod 104 which carries at its opposite end one member of the universal joint 106. The other member of the universal joint 186 is secured to the shaft 108 which is carried in the bearing 110 and which has on its end the sprocket 112. The sprocket 112 is driven by the chain drive 114 which is coupled to the sprocket 116 of the gear box 118 which is driven by the motor 120.

The pair of universal joints 98 and 106 and the relatively telescoping motion of the coupling rods 180 and 104 in the spline coupling 102 enables the feeder 84 to be rcciprocated, as shown in phantom line in FIGURE 2, while the knurled driver 86 is being rotated due to the action of the chain drive 114 on the sprocket 112.

The feed duct 94 is supported by the guide 122 which is carried on the free end of the shaft 46. The front portion of the feed duct 94 is provided with the cooling coil 124 through which liquid coolant may be introduced. The cooling coil 124 prevents the feeding portion of the feed duct 94 which is disposed within the processing chamber 82 from becoming overheated. This is necessary as melting of the aluminum wire 38 within the feed duct 94 must be avoided for the satisfactory operation of the apparatus of the present invention.

A shield 126 formed of high melting metal may be provided on the feeding portion of the feed duct 94 at the side thereof adjacent the boat or crucible 128 in which the molten aluminum obtained from the melting of the aluminum wire 38 discharged from the feeding portion of the feed duct 94 is carried.

The shield 126 is interposed between the boat 128 and the discharge end 130 of the feed duct 94. The shield '126 is carried on the posts 132 which are fixedly secured to the sides of the feed duct 94 in the region of its feeding portion adjacent its discharge end 130. Thus, the posts 132 may be secured to the outside wall surface of the feed duct 94 as by welding or brazing, or clamping, provided that the weldment or brazement is capable of withstanding high temperatures.

The relative distance between the discharge end 130 and the shield 126 may be selectively adjusted as will be explained below to meet specific requirements.

The shield 126 is provided with an aperture 134 which is in spaced alignment to the discharge end 130 of the feed duct 94. This enables aluminum wire 38 discharged from the discharge end 130 of the feed duct 94 to pass through the shield 126 into the boat 128.

The shield 126 has a sufiicient length to protect the discharge end 130 and the immediate region at all sides of such discharge end 130 including the region in which the posts 132 are secured to the feed duct 94 from the adverse affects of aluminum depositing from the boat 128 on the feed duct 94.

The boat 128, which may comprise one or more boats in series or other disposition, is of conventional construction, and may be formed from boron nitride or other refractory, provided with conducting material, so that the boat 128 may be heated to a temperature suflicient to effect the boiling of the aluminum introduced to it from the aluminum wire 38. Thus, the boat 128 may be carried on standards 136 and 138 within the processing chamber 82. The standards 136 and 138 are provided with electrical conduits 140 and 142 for effecting heating of the boat 128.

The discharge end 130 of the feed duct 94 with its associated shield 126 is spaced adjacent boat 128 as 4 dictated by the process requirements (see in particular FIGURE 3).

The regulation of the distance of the shield 126 from the boat 128, and the size of the posts 132 and the distance which they project beyond the feed duct 94 permit closely limiting the extent of deposition of aluminum on the feeding portion of the feed duct about the discharge end thereof.

Thus, the temperature of the molten aluminum being vaporized within the boat will be of the order of 1,800 C. The temperature of the shield 126 must be sufiiciently high so aluminum will deposit thereon and remain in the liquid state. This can be accomplished by maintaining the temperature of the shield within the range between the melting point and the boiling point of aluminum, namely between about 659 C. and l,800 C.

The shield 126 will be heated by virtue of its disposition closely adjacent the boat 128. Its temperature will be in turn dependent upon such distance, and on the diameter of the posts 132, their number, and their conductivity. Since the relative position of the shield 126 in relation to the duct 94 and boat 128 can be selectively regulated, precise control of the temperature of the shield 126 can be accomplished.

By maintaining the shield 126 at a temperature below the boiling point of the aluminum being vaporized and below its vaporization temperature, aluminum vaporized from the boat 128 will be condensed on shield 126 away from the discharge end 130 of the feed duct 94, thereby not clogging such feed duct 94.

While it is possible to provide independent heating of the shield 126 as by the provision of electrical conduits running thereto, the same is normally not necessary, since satisfactory heating of the shield 126 can be effected due to the radiation of heat from the boat 128. Where desired, the disposition of the liquid particles from the shield 126 may be regulated so that they reenter the boat 128 or fall onto the feed Wire 38 by positioning the location of the shield 126 in respect to the boat 128 or feed Wire 38. An embodiment in which the coating metal liquid particles are recaptured after having dripped from shield 126 by being caught within boat 128 is shown in FIG- URE 6.

A coolant tray 143 is carried on the standards 136 and 138 at a spaced distance beneath the boat 128 to protect the mechanical and electrical parts therebelow from thermal radiation and haphazard diffusion of vaporized aluminum about the bottom portion of the processing chamber 82.

By moving the discharge end 130 of the feed duct 94 along the length of the boat 128, engagement of the aluminum with the boat is along the length of the boat rather than in a localized area. This both facilitates in the vaporization of the aluminum and also increases the life of the boat, since the wear at the region of the engagement of the boat with the aluminum wire 38 is dispersed over a wide area rather than localized.

The outer vessel 10 is provided with a shelf 144 having a slot 146 disposed above the boat 128. As seen in FIG- URE 1, the slot 146 may have a width somewhat larger than the boat 128, since the metal being vaporized will leave the boat 128 along a path which will diverge from the ends of the boat as well as include the region directly above the boat (see phantom lines in the right portion of FIGURE 1).

The material to be coated, which may be paper, foil, plastic, etc. is shown in the illustrated embodiment as comprising a web 148, such as a web of plastic like Mylar.

A wide variety of means may be used to feed the web 148 over the slot 146, and no claim of invention is made in the present application for any particular means to do so. In the illustrated embodiment, the web 148 is carried between two rollers, one roller 150 being shown, with one of the rollers, namely the roller 150 being rotated by the motor 152.

The apparatus of the present invention enables prolonged runs to be made. Thus, the metal to be vaporized may be continuously fed into the boat 128 at the same rate at which such metal is being vaporized, so that a constant inventory of molten metal may be maintained within the boat 128. Since the apparatus of the present invention provides for both long life of the boat 128 and avoidance of clogging of the discharge end 130 of the feed duct 94, the apparatus may function for extended periods of time without the necessity for ceasing production to replace either the boat 128 or the feed duct 94 (the two most common causes of failure in prior vacuum coating equipment being the failure of the boat which was largely due to the localized introduction of the aluminum wire, or the clogging of the discharge end of the feed duct due to deposition of vaporized metal thereon and condensation of such vaporized metal on the cooled feed duct).

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

I claim:

1. Vacuum coating apparatus for coating a metal onto an article including a vacuum chamber containing an open heated boat for vaporizing the coating metal, and feeding means for feeding coating metal to said open boat, said feeding means including a feed duct through which a wire of the coating metal is fed to the boat, with the discharge end of said duct being spaced adjacent said boat, the discharge end of said duct being spaced laterally from the longitudinal axis of said boat, and a shield secured to said duct and spaced intermediate said boat and the discharge end of said duct, said shield being of sufficient size to block access of vaporized coating metal to the discharge end of the feed duct and the portion of the feed duct adjacent to the discharge end, with said shield having an aperture therein which is in alignment with the discharge end of the duct through which the wire 6 of coating metal from the duct may be fed to the open boat, said shield being mounted on heat-conducting members which are fixedly secured to the feed duct, and with said heat-conducting members carrying away heat from said shield.

2. Vacuum coating apparatus for coating a metal onto an article including a vacuum chamber containing an open heated boat for vaporizing the coating metal, and feeding means for feeding coating metal to said open boat, said feeding means including a feed duct through which the wire of the coating metal is fed to the boat, said feeding means being operative to feed wire passing therethrough in a plane parallel to the longitudinal axis of said boat, with the discharge end of said duct being spaced adjacent said boat, the discharge end of said duct being spaced laterally from the longitudinal axis of said boat, a shield secured to said duct and spaced intermediate said boat and the discharge end of said duct, said shield being of sufficient size to block access of vaporized coating metal to the discharge end of the feed duct and the portion of the feed duct adjacent to the discharge end, with said shield having an aperture therein which is in alignment with the discharge end of the duct through which the Wire of coating metal from the duct may be fed to the open boat, said shield being in such close proximity to the open boat that when metal is vaporized from said boat, said shield is heated above the melting temperature of the metal being vaporized by radiant heat from said boat, said shield being positioned above the boat in such disposition that liquid particles on the face of the shield drop therefrom into the boat.

References Cited in the file of this patent UNITED STATES PATENTS 2,587,036 Germer et a1. Feb. 26, 1952 2,635,579 Chadsey Apr. 21, 1953 2,664,853 Schuler Jan. 5, 1954 2,691,814 Tait Oct. 19, 1954 2,715,617 White Aug. 16, 1955 2,914,643 Fields Nov. 24, 1959 2,922,869 Giannini et al. Jan. 26, 1960 

1. VACUUM COATING APPARATUS FOR COATING A METAL ONTO AN ARTICLE INCLUDING A VACUUM CHAMBER CONTAINING AN OPEN HEATED BOAT FOR VAPORIZING THE COATING METAL, AND FEEDING MEANS FOR FEEDING COATING METAL TO SAID OPEN BOAT, SAID FEEDING MEANS INCLUDING A FEED DUCT THROUGH WHICH A WIRE OF THE COATING METAL IS FED TO THE BOAT, WITH THE DISCHARGE END OF SAID DUCT BEING SPACED ADJACENT SAID BOAT, THE DISCHARGE END OF SAID DUCT BEING SPACED LATERALLY FROM THE LONGITUDINAL AXIS OF SAID BOAT, AND A SHIELD SECURED TO SAID DUCT AND SPACED INTERMEDIATE SAID BOAT AND THE DISCHARGE END OF SAID DUCT, SAID SHIELD BEING OF SUFFICIENT SIZE TO BLOCK ACCESS OF VAPORIZED COATING METAL TO THE DISCHARGE END OF THE FEED DUCT AND THE PORTION OF THE FEED DUCT ADJACENT TO THE DISCHARGE END, WITH SAID SHIELD HAVING AN APERTURE THEREIN WHICH IS IN ALIGNMENT WITH THE DISCHARGE END OF THE DUCT THROUGH WHICH THE WIRE OF COATING METAL FROM THE DUCT MAY BE FED TO THE OPEN BOAT, SAID SHIELD BEING MOUNTED ON HEAT-CONDUCTING MEMBERS WHICH ARE FIXEDLY SECURED TO THE FEED DUCT, AND WITH SAID HEAT-CONDUCTING MEMBERS CARRYING AWAY HEAT FROM SAID SHIELD. 